The Traffic Calming Program (TCP) undertook a streamlined speed bump project in the Summer of 1996 to address traffic problems identified by residents along SE 46th Avenue from Steele Street to Woodstock Boulevard.
The goal of the project was to enhance street safety by reducing the 85th percentile speed of vehicles using SE 46th Avenue closer to the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are the only devices considered for streets like SE 46th Avenue, which are classified as Local Service Streets, are not transit or primary fire response routes, and have vehicle volumes between 400 and 1700 vehicles per day. Speed bumps are effective tools to reduce vehicle speed without affecting access. It is not an intended goal to reduce traffic volume on low-volume Local Service Streets.
SE 46th Avenue serves a single family residence neighborhood with commercial use at its south end. SE Steele, to the north, and Woodstock Boulevard, at SE 46th Avenue's south end, are both Neighborhood Collector streets. SE 46th Avenue has sidewalks and curbs. A large portion of the daily traffic on SE 46th Avenue is believed to be cut-through traffic due to the commercial uses and a traffic signal at Woodstock.
All residents along SE 46th Avenue were invited to an open house September 5, 1996 to review and comment on the proposed speed bump installation. Four households were represented at the open house. Those who attended expressed approval for the proposed project. A petition was available at the open house for residents along SE 46th Avenue to sign and was circulated after the open house by a local resident. Of the 44 households along the street, 32, or 72.7%, signed the petition requesting speed bump installation.
Four 14-foot speed bumps, at 450 to 500 foot spacing, were constructed along the 0.32 mile stretch of SE 46th Avenue, Steele Street to Woodstock Boulevard, on May 10, 1997 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously spread between 23 and 31 mph, have been shifted into the range of 20 to 25 mph. The 85th percentile vehicle speed before the project was 29.8 mph. After bump construction the average 85th percentile speed is 25 mph and ranges from a low of 20 mph (near the bumps) to a high of 27 mph. Before installation of the speed bumps 48% of drivers exceeded the posted speed limit of 25 mph and 2% exceeded the limit by 10 mph or more. Since bump construction 11.8% of drivers exceed the posted speed limit and 0.15% exceed the limit by 10 mph or more.
Traffic volumes measured before bump construction was 980-1200 vehicles per day (vpd). After bump construction volumes measured 1150-1350 vpd. Traffic volumes measured on side streets adjacent to SE 46th Avenue showed no significant increases from volumes measured before speed bump construction.
Traffic Calming on SE 46th Avenue, Steele Street to Woodstock Boulevard has successfully reduced the 85th percentile closer to the posted speed and enhanced street safety and livability.